proof-quality bullion (platinum, silver, gold) coins released by the United States Mint beginning in October 1986.
Their production process, on specially adapted coining presses and specially polished dies, brings forth even the most minute of details with remarkable clarity.

American Numismatic Association (ANA):

nonprofit educational organization that encourages the study of money throughout the world.

annealing:

heating blanks (planchets) in a furnace that softens the metal.

assay:

to analyze and determine the purity of metal.

bag mark:

a mark on a coin from contact with other coins in a mint bag.

bi-metallic:

a coin comprised of two different metals, bonded together.

blank:

another word for planchet, the blank piece of metal on which a coin design is stamped.

bullion:

platinum, gold or silver in the form of bars or other storage shapes, including coins and ingots.

bullion coin:

precious metal coin traded at current bullion prices.

business strike:

a coin produced for general circulation (as opposed to a proof or uncirculated coin specially made for collectors).

bust:

a portrait on a coin, usually including the head, neck and upper shoulders.

clad coinage:

coins that have a core and outer layer made of different metals.
Since 1965, all circulating U.S. dimes, quarters, half dollars and dollars have been clad.

coin:

flat piece of metal issued by the government as money.

collar:

a metal piece that restrains the expanding metal of a planchet during striking.

commemorative:

a special coin or medal issued to honor an outstanding person, place or event.

condition:

the physical state of a coin.

counterfeit:

a fake coin or other piece of currency made so that people will think it's genuine.

currency:

any kind of money - coins or paper money - that's used as a medium of exchange.

denomination:

the different values of money.
U.S. coins currently are made in the following six denominations:
cent, nickel, dime, quarter, half dollar and dollar.

die:

an engraved stamp used for impressing a design (images, value and mottoes) upon a blank piece of metal to make a coin.

designer:

the artist who creates a coin's design (but doesn't necessarily engrave the design into a coinage die).

edge:

the outer border of a coin, considered the "third side" (not to be confused with "rim").
Some coins feature lettering, reeding, or ornamental designs on their edges.

engraver:

an artist who sculpts a claymodel of a coin's design in bas relief.

error:

an improperly produced coin, that was overlooked in production, and later released into circulation.

face value:

the sum for which a coin can be spent or exchanged (a dime's face value is 10¢) as opposed to its collector or precious metal value.

a specially produced coin made from highly
polished planchets and dies and often struck more than once to accent the design.
Proof coins receive the highest quality strike possible
and can be distinguished by their mirror-like background and frosted foreground.

proof set:

a complete set of proof coins of each denomination made in a year.

relief:

the part of a coin's design that is raised above the surface, opposite of incuse.

restrike:

a coin that is minted using the original dies but at a later date.

reverse:

the back (or "tails") side of a coin.

riddler:

a machine that screens out blanks (planchets) that are the wrong size or shape.

rim:

the raised edge on both sides of a coin (created by the upsetting mill) that helps protect the coin's design from wear.

roll:

coins packaged by banks, dealers or the United States Mint.
The number of coins in a roll depends on the denomination:
50 cents, 40 nickels, 50 dimes, 40 quarters, 20 half dollars, or 25 dollars.

series:

a collection of coins that contains all date and mint marks of a specific design and denomination.
For example, a Kennedy series would include a Kennedy half dollar from each year from each Mint facility (Philadelphia, Denver, San Francisco), beginning with the coins first issued in 1964.

slab:

nickname for some protective coin encapsulation methods, especially those that are permanently sealed and rectangular.

strike:

the process of stamping a coin blank with a design.
The strength of the imprint - full, average, or weak - affects the value of rare coins.

type set:

a collection of coins based on denomination.
For example, a nickel type set would contain one of each of the four types of nickels that the United States Mint has produced.

The term "uncirculated" may have three different meanings when applied to a coin.

First, it can refer to the particular manufacturing process by which a coin is made.

Second, it can be used as a grade when referring to a coin's degree of preservation and quality of the strike.

Or third, "uncirculated" can point to the fact that a coin has not been used in everyday commerce.

At the United States Mint, we use the term uncirculated when referring to the special coining process used to make the coin,
which gives it a brilliant finish.
Uncirculated coins are manufactured using the same process as circulating coins, but with quality enhancements such as slightly higher coining force, early strikes from dies,
special cleaning after stamping, and special packaging.
Uncirculated coins may vary to some degree because of blemishes, toning, or slight imperfections.

upsetting mill:

a machine that raises the rim on both sides of a blank (planchet)

variety:

a minor change from the basic design type of a coin.

year set:

a collection of all coins issued by a country for any one year (does not necessarily include every mint mark).